swift - Highlight a specific part of the text in SwiftUI

Question

Hello I'm new to Swift and am using SwiftUI for my project where I download some weather data and I display it in the ContentView().

I would like to highlight some part of the Text if it contains some specific word, but I don't have any idea how to start.

In ContentView(), I have tried to set a function receiving the string downloaded from web and return a string. I believe this is wrong, because SwiftUI does not apply the modifiers at the all for the Text.

For example, in my ContentView() I would like the word thunderstorm to have the .bold() modifier:

struct ContentView: View {
  let testo : String = "There is a thunderstorm in the area"

  var body: some View {
    Text(highlight(str: testo))
  }

  func highlight(str: String) -> String {
    let textToSearch = "thunderstorm"
    var result = ""

    if str.contains(textToSearch) {
      let index = str.startIndex
      result = String( str[index])
    }

    return result
  }

}

Answer 1

If that requires just simple word styling then here is possible solution.

Tested with Xcode 11.4 / iOS 13.4

struct ContentView: View {
    let testo : String = "There is a thunderstorm in the area. Added some testing long text to demo that wrapping works correctly!"


    var body: some View {
        hilightedText(str: testo, searched: "thunderstorm")
            .multilineTextAlignment(.leading)
    }

    func hilightedText(str: String, searched: String) -> Text {
        guard !str.isEmpty && !searched.isEmpty else { return Text(str) }

        var result: Text!
        let parts = str.components(separatedBy: searched)
        for i in parts.indices {
            result = (result == nil ? Text(parts[i]) : result + Text(parts[i]))
            if i != parts.count - 1 {
                result = result + Text(searched).bold()
            }
        }
        return result ?? Text(str)
    }
}

Note: below is previously used function, but as commented by @Lkabo it has limitations on very long strings

func hilightedText(str: String) -> Text {
    let textToSearch = "thunderstorm"
    var result: Text!

    for word in str.split(separator: " ") {
        var text = Text(word)
        if word == textToSearch {
            text = text.bold()
        }
        result = (result == nil ? text : result + Text(" ") + text)
    }
    return result ?? Text(str)
}